Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$181.81	8.104%	$196.5439	$196.54	$196.55	$196.50
Purchase #2	$75.44	5.238%	$79.3915	$79.39	$79.40	$79.40
Purchase #3	$224.65	4.636%	$235.0648	$235.06	$235.05	$235.10
Purchase #4	$81.68	11.252%	$90.8706	$90.87	$90.85	$90.90
Purchase #5	$156.50	3.788%	$162.4282	$162.43	$162.45	$162.40
Purchase #6	$157.97	5.562%	$166.7563	$166.76	$166.75	$166.80
Purchase #7	$6.51	13.803%	$7.4086	$7.41	$7.40	$7.40
7 purchase totals =	$884.56		$938.4639	$938.46	$938.45	$938.50